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8.75 rear pinion splines #448086 08/24/09 02:23 PM 08/24/09 02:23 PM
Joined: May 2005 Posts: 84 NC B Badfish67 OP member
Badfish67 OP member B Joined: May 2005 Posts: 84 NC	Which is a stronger pinion spline, the 10 or the 29...or does it not matter? 1967 Barracuda 360ci/727 9.723ET @139.44mph

Re: 8.75 rear pinion splines [Re: Badfish67] #448087 08/24/09 03:52 PM 08/24/09 03:52 PM
Joined: Jan 2003 Posts: 5,894 Florida Locomotion master
Locomotion master Joined: Jan 2003 Posts: 5,894 Florida	I've never known it to matter. The 10 spline are much more common in the aftermarket performance gear ratios. The weakest part of an 8 3/4" rear are the gear teeth.

Re: 8.75 rear pinion splines [Re: Badfish67] #448088 08/24/09 03:59 PM 08/24/09 03:59 PM
Joined: Jul 2006 Posts: 4,595 On the south side of Nowhere S S/ST 3040 master
S/ST 3040 master S Joined: Jul 2006 Posts: 4,595 On the south side of Nowhere	Typically, fine spline is always stronger..........unfortunately, not the weak link on an 8 3/4" rear end so, in this case even though the 29 spline is technically stronger, it doesn't matter.

Re: 8.75 rear pinion splines [Re: S/ST 3040] #448089 08/24/09 05:04 PM 08/24/09 05:04 PM
Joined: Aug 2003 Posts: 43,228 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,228 Bend,OR USA	Quote: Typically, fine spline is always stronger..........unfortunately, not the weak link on an 8 3/4" rear end so, in this case even though the 29 spline is technically stronger, it doesn't matter. I would, and do, use the "742" case as it has the thickess pinion stem at the yoke If your going to put a lot of power to this third member with good traction make sure and replace the stock driver side carrier cap with a steel cap from Mark Williams or Summer Bros. Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: 8.75 rear pinion splines [Re: Cab_Burge] #448090 08/24/09 05:21 PM 08/24/09 05:21 PM
Joined: May 2005 Posts: 84 NC B Badfish67 OP member
Badfish67 OP member B Joined: May 2005 Posts: 84 NC	Thanks for the info, but I think your wrong about the 742 being the thickest. The 742 has a 1 3/4" pinion shaft and the 489 has a 1 7/8" shaft. 1967 Barracuda 360ci/727 9.723ET @139.44mph

Re: 8.75 rear pinion splines [Re: Badfish67] #448091 08/24/09 05:29 PM 08/24/09 05:29 PM
Joined: Apr 2005 Posts: 12,271 Overpriced Housing Central RobX4406 I Live Here
RobX4406 I Live Here Joined: Apr 2005 Posts: 12,271 Overpriced Housing Central	Quote: Thanks for the info, but I think your wrong about the 742 being the thickest. The 742 has a 1 3/4" pinion shaft and the 489 has a 1 7/8" shaft. You're talking about the other end of the pinion. Cab is talking about the yoke end, where the nut goes, the shaft/Bearing surface is larger in that area on a 742 vs a 741 or 489.

Re: 8.75 rear pinion splines [Re: RobX4406] #448092 08/24/09 06:31 PM 08/24/09 06:31 PM
Joined: May 2004 Posts: 3,210 robin hood country deaks master
deaks master Joined: May 2004 Posts: 3,210 robin hood country	Dr Diff, has posted pics of them all in the tech section here. 69 Dart GTS 440 mopar .590 cam, Edelbrock heads, 3200# best et 6.45, 106.78, 10.14, 132.88 mph, 1.47 60ft best 60ft 1.36

Re: 8.75 rear pinion splines [Re: RobX4406] #448093 08/24/09 07:45 PM 08/24/09 07:45 PM
Joined: Jan 2003 Posts: 8,016 Polson, MT DoctorDiff master
DoctorDiff master Joined: Jan 2003 Posts: 8,016 Polson, MT	All 3 designs share the same front pinion diameter. Contact info

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